Revert "[clang][Modules] Reporting Errors for Duplicating Link Declarations in modulemaps (llvm#148959)"

This reverts commit 538e9e8.

Author: qiongsiwu

clang/include/clang/Basic/DiagnosticLexKinds.td

@@ -912,11 +912,6 @@ def err_mmap_nested_submodule_id : Error<
   "qualified module name can only be used to define modules at the top level">;
 def err_mmap_expected_feature : Error<"expected a feature name">;
 def err_mmap_expected_attribute : Error<"expected an attribute name">;
-def warn_mmap_link_redeclaration : Warning<"redeclaration of link library '%0'">,
-  InGroup<DiagGroup<"module-link-redeclaration">>, DefaultError;
-def note_mmap_prev_link_declaration : Note<"previously declared here">;
-def err_mmap_submodule_link_decl
-    : Error<"link declaration is not allowed in submodules">;
 def warn_mmap_unknown_attribute : Warning<"unknown attribute '%0'">,
   InGroup<IgnoredAttributes>;
 def warn_mmap_mismatched_private_submodule : Warning<

clang/lib/Lex/ModuleMapFile.cpp

@@ -118,8 +118,7 @@ struct ModuleMapFileParser {
   std::optional<ExcludeDecl> parseExcludeDecl(clang::SourceLocation LeadingLoc);
   std::optional<UmbrellaDirDecl>
   parseUmbrellaDirDecl(SourceLocation UmbrellaLoc);
-  std::optional<LinkDecl>
-  parseLinkDecl(llvm::StringMap<SourceLocation> &SeenLinkDecl, bool Allowed);
+  std::optional<LinkDecl> parseLinkDecl();
 
   SourceLocation consumeToken();
   void skipUntil(MMToken::TokenKind K);
@@ -326,7 +325,6 @@ std::optional<ModuleDecl> ModuleMapFileParser::parseModuleDecl(bool TopLevel) {
   SourceLocation LBraceLoc = consumeToken();
 
   bool Done = false;
-  llvm::StringMap<SourceLocation> SeenLinkDecl;
   do {
     std::optional<Decl> SubDecl;
     switch (Tok.Kind) {
@@ -407,9 +405,7 @@ std::optional<ModuleDecl> ModuleMapFileParser::parseModuleDecl(bool TopLevel) {
       break;
 
     case MMToken::LinkKeyword:
-      // Link decls are only allowed in top level modules or explicit
-      // submodules.
-      SubDecl = parseLinkDecl(SeenLinkDecl, TopLevel || MDecl.Explicit);
+      SubDecl = parseLinkDecl();
       break;
 
     default:
@@ -826,8 +822,7 @@ ModuleMapFileParser::parseUmbrellaDirDecl(clang::SourceLocation UmbrellaLoc) {
 ///
 ///   module-declaration:
 ///     'link' 'framework'[opt] string-literal
-std::optional<LinkDecl> ModuleMapFileParser::parseLinkDecl(
-    llvm::StringMap<SourceLocation> &SeenLinkDecl, bool Allowed) {
+std::optional<LinkDecl> ModuleMapFileParser::parseLinkDecl() {
   assert(Tok.is(MMToken::LinkKeyword));
   LinkDecl LD;
   LD.Location = consumeToken();
@@ -843,33 +838,12 @@ std::optional<LinkDecl> ModuleMapFileParser::parseLinkDecl(
   if (!Tok.is(MMToken::StringLiteral)) {
     Diags.Report(Tok.getLocation(), diag::err_mmap_expected_library_name)
         << LD.Framework << SourceRange(LD.Location);
-    consumeToken();
     HadError = true;
     return std::nullopt;
   }
 
-  StringRef Library = Tok.getString();
-
-  LD.Library = Library;
+  LD.Library = Tok.getString();
   consumeToken();
-
-  // Make sure we eat all the tokens when we report the errors so parsing
-  // can continue.
-  if (!Allowed) {
-    Diags.Report(LD.Location, diag::err_mmap_submodule_link_decl);
-    HadError = true;
-    return std::nullopt;
-  }
-
-  auto [It, Inserted] =
-      SeenLinkDecl.insert(std::make_pair(Library, LD.Location));
-  if (!Inserted) {
-    Diags.Report(LD.Location, diag::warn_mmap_link_redeclaration) << Library;
-    Diags.Report(It->second, diag::note_mmap_prev_link_declaration);
-    HadError = true;
-    return std::nullopt;
-  }
-
   return std::move(LD);
 }